1. Technical Field
This invention involves a programmable electronic time lock, especially for use in controlling the opening of vaults, and also a method for operating the lock.
2. Description of Related Art
Security is naturally of the utmost importance in the design of locking systems for such restricted access areas as bank vaults. There are accordingly a large number of mechanical and electro-mechanical locking devices. One problem with existing lock systems is that the more secure they are, the more complex they are, and authorized users are constrained by the locks either to accept fixed opening times, complicated time-changing procedures, or poor overview of the status of the lock.
Some devices have attempted to address certain of these drawbacks by taking advantage of more modern electronic and electro-mechanical components. Such existing electronic devices are disclosed in U.S. Pat. No. 4,875,351 (Evans et al., Oct. 24, 1991); PCT application PCT/EP36/00133 (Skye, S. A., published on Sep. 12, 1986 as WO 86/05230); and PCT application PCT/CH91/00111 (Ciposa Microtechniques, S. A., published on Nov. 28, 1991 as WO 91/18168).
The existing devices suffer from several additional disadvantages. First, the more modern, electronic time locks typically do not match existing mechanical movements with respect to size or mounting. As such, retro-fitting more modern designs is either impossible or unduly expensive. Second, most existing designs do not allow the user to set the actual time or to monitor the actual time when the vault door is open. Third, existing lock systems do not allow the user to program opening times for a full seven-day week and to monitor the opening times; ideally, the locking system should display to the authorized user not only the status of all seven days of the weeks, but also the specific day and time of the next programmed opening.
One other drawback of existing lock systems is that they make it difficult or impossible to change opening times without completely resetting the mechanism. In order to accommodate temporary deviations from the normal opening routine, the user should be able to change the opening time within a given day, or to change the opening schedule for a given day of the week, without having to reset the main schedule for the system. This may, for example, be necessary on days in which the bank is to open later than normal, or when the bank will not be opening at all because of a holiday. Furthermore, the lock system should be able to accommodate changes to and from "day light savings time" or "summer time" without the user having to reset the entire schedule by one hour. Accordingly, it should be possible to change the real time setting of the system by plus or minus one hour and 59 minutes (for most countries, only one-hour changes are ever required).
The object of this invention is to provide a programmable time lock that avoids the shortcomings and provides the needed features mentioned above.